Strip line to coaxial transition



April 5, 1966 c. o. FORGE 3,245,013

STRIP LINE T0 COAXIAL TRANSITION Filed Dec. 25, 1964 Figure 2 INVENTOR CHARLES o. FORGE BY Q-C- Wk ATTORNEY United States Patent 3,245,013 STRIP LINE T0 COAXHAL TRANSITEON Charles 0. Forge, Cupertino, Calif., assigncr to Hewlett- Packard ornpany, Pain Alto, Caiifi, a cnrporation of Caiifornia Fiied Dec. 23, 1964, Ser. No. 420,686 3 Claims. (Cl. 333-84) This invention relates to means for coupling a strip line to a coaxial line to provide a low reflection transition.

It is an object of the present invention to provide apparatus for reducing discontinuities in the electric field distribution about the connection of a strip line to a coaxial line.

It is another object of the present invention to provide an improved, W reflection transition from strip line to coaxial line.

In accordance with the illustrated embodiment of the present invention, the center conductor of a coaxial line terminates near the plane of a strip line. The strip line is divided into n number of secondary strip lines, each of which divides into m number of auxiliary strip lines which are radially disposed about and in contact with the center conductor of the coaxial line. The mean signal path lengths from the center corductor through the auxiliary and secondary strip lines to the main strip line are equal.

These and other objects will be apparent from a reading of this specification and inspection of the accompanying drawing in which:

FIGURE 1 is a perspective view of the transition from strip line to coaxial line; and

FIGURE 2 is a sectional view of the transition of FIGURE -1.

Referring now to the figures of the drawing, there is shown a slab of dielectric material 9 supporting a conductor 11 above a ground plane 13 to form a strip line electric wave conductor having a characteristic impedance Z0. A coaxial cable 14 including inner conductor 15 and outer conductor 17 is disposed normal to the strip line with the inner conductor 15 terminating about in the plane of the conductor 11. The outer conductor 17 is connected to the ground plane 13. A plurality of auxiliary strip lines 19, 21, 23 and 25, each having a characteristic impedance 4Z0, are radially disposed about the terminal end of center conductor 15 in contact with it. Pairs of the auxiliary strip lines combine in parallel to form secondary strip lines, each having a characteristic impedance of 220. The secondary lines combine in parallel and connect to the main strip line which has a characteristic impedance of Z0. The radial orientation of the auxiliary lines 1945 about the center conductor 15 enables an electric signal Wave to propagate radially along the lines and hence establish at their junction with conductor 15 a radial electric field similar to the field which exists in the coaxial cable 14 about the center conductor. The field transition may be improved further by rounding the corner of the ground conductor connection and by radially filleting the center conductor 15 near the contact with strip conductor 11, as shown in FIGURE 2. Also, the mean signal path length from the terminal end of the center conductor 15 along the auxiliary and secondary strip lines to the main strip line are all equal, thus eliminating out-of-phase signal cancellation and mismatch. It should be understood that other configurations using various numbers of auxiliary strip lines, say five or eight, radially disposed about the center conductor may also be used in accordance with the present invention.

Therefore, the transition from strip line to coaxial line according to the present invention decreases signal re flections and signal losses by shaping the electric field about the strip line near the transition to conform to the electric field in the coaxial line and by maintaining the mean signal path lengths substantially equal.

I claim:

1. Electrical conductor connection apparatus comprismg:

a main strip line electric wave conductor including a ground conductor and having a characteristic impedance;

a coaxial line electric wave conductor including a cen ter conductor and an outer conductor;

said main strip line and coaxial line electric wave conductors being disposed in intersecting skew relationship;

means connecting together said ground conductor and said outer conductor;

a plural number, n, of auxiliary strip line electric wave conductors connected to said center conductor and radially disposed thereabout; and

means connecting said auxiliary strip lines to said main strip line.

2. Apparatus as in claim 1 wherein:

each of said auxiliary strip lines has a characteristic impedance equal to n times the characteristic impedance of the main strip line.

3. Electrical conductor connection appartus comprisa main strip line electric Wave conductor including a ground conductor and having a characteristic impedance;

a coaxial line electric wave conductor including a center conductor and an outer conductor;

said main strip line and coaxial line electric wave conductors being disposed in intersecting skew relationship;

means connecting together said ground conductor and said outer conductor;

a plurality of auxiliary strip line electric wave conductors connected to said center conductor and radially disposed thereabout; and

secondary strip line electric Wave conductors connecting selected ones of said auxiliary strip lines and said main strip line. 

1. ELECTRICAL CONDUCTOR CONNECTOR APPARATUS COMPRISING: A MAIN STRIP LINE ELECTRIC WAVE CONDUCTOR INCLUDING A GROUND CONDUCTOR AND HAVING A CHARACTERISTIC IMPEDANCE; A COAXIAL LINE ELECTRIC WAVE CONDUCTOR INCLUDING A CENTER CONDUCTOR AND AN OUTER CONDUCTOR; SAID MAIN STRIP LINE AND COAXIAL LINE ELECTRIC WAVE CONDUCTORS BEING DISPOSED IN INTERSECTING SKEW RELATIONSHIP; MEANS CONNECTING TOGETHER SAID GROUND CONDUCTOR AND SAID OUTER CONDUCTOR; A PLURAL NUMBER, N, OF AUXILIARY STRIP LINE ELECTRIC WAVE CONDUCTORS CONNECTED TO SAID CENTER CONDUCTOR AND RADIALLY DISPOSED THEREABOUT; AND MEANS CONNECTING SAID AUXILIARY STRIP LINES TO SAID MAIN STRIP LINE. 